Embodiments of the present invention relate to sputtering material on a substrate in a sputtering chamber.
A sputtering chamber is used to sputter material onto a substrate to manufacture electronic circuits, such as for example, integrated circuits and displays. Typically, the chamber comprises an enclosure wall that encloses a process zone into which a gas is introduced, a gas energizer to energize the gas at least initially during the sputtering process, and an exhaust conduit from which the gases and other species are exhausted and which has a throttle valve to control the pressure in the chamber. The chamber is used to sputter deposit a material from a sputtering target onto the substrate, such as a metal, for example, aluminum, copper, titanium, tantalum or tungsten; or a metal compound, such as for example, tantalum nitride, tungsten nitride or titanium nitride.
In conventional sputtering processes, the yields from the substrate are reduced when particles flake off from the chamber walls and deposit on the substrate during the sputtering process. This arises when sputtered material accumulate on the exposed surfaces of walls and components about the substrate. After a number of sputtering cycles, the accumulated sputtered material becomes thick and it flakes off and deposits as flaked particles on the substrate. The deposited flaked particles cause additional sputtered material deposited on the substrate to deposit conformally over the flakes forming irregularities that short the circuitry being fabricated on the substrate.
In conventional processes, periodically, the sputtering residues are cleaned off from the surfaces inside the chamber, such as for example, the surfaces of the deposition shields and walls surrounding the substrate, to reduce their accumulated thickness and reduce the number of particles flaking off the walls. The chamber may be cleaned by a wet-cleaning process in which the chamber is shut down and an operator scrubs the chamber walls with an acid or solvent. However, the wet cleaning process often varies in quality and thoroughness from session to session perhaps because it is manually performed. The chamber may also be cleaned by a dry-cleaning process in which plasma or microwave-activated cleaning gas is provided in the chamber. However, the cleaning gas is sometimes slow at cleaning-off some types of deposits, for example, those which are relatively thick or which have a chemical composition that is hard to clean. More importantly, the chamber downtime that occurs during the wet or dry cleaning process reduces processing throughput and increases substrate costs, which in the semiconductor and display fabrication industries are highly undesirable. Thus, it is desirable to reduce chamber downtime by processing a larger number of substrates in the chamber without cleaning the chamber.
Thus, it is desirable to have a method of sputter depositing material on a substrate that is capable of reducing the number of flaked-off particles deposited on the substrate even after a large number of process cycles are performed in the chamber. It is further desirable to be able to use the chamber to process a large number of substrates with good yields and without requiring frequent chamber downtime for cleaning.